Fluid to electric transducer



June 2,1970 QBBEEKEN 3,515,827

FLUID TO ELECTRIC TRANSDUCER Filed March 20, 1968 26 25 H I0 I I l ['6 P mr Am. 1 18 WA 0 Fm l 42 43 2st 5A 27 INVENTOR. BASIL B. BEE/(EN United States Patent 3,515,827 FLUID TO ELECTRIC TRANSDUCER Basil B. Beeken, New Haven, Conn., assignor to Pitney- Bowes, Inc., Stamford, Conn., a corporation of Delaware Filed Mar. 20, 1968, Ser. No. 721,541 Int. Cl. H01h 35/24, 35/28, 35/40 US. Cl. 200--81.9 4 Claims ABSTRACT OF THE DISCLOSURE A fluid to electric transducer including a glass-enclosed reed-type switch that has a pair of magnetically sensitive contacts. An annular permanent magnet is mounted for sliding movement over a cylindrical outer surface of the glass enclosure and is arranged so as to be displaced in one axial direction by a first fluid-operated means, and to be displaced in the other axial direction by a second fluid-operated means.

This invention relates to an improved fluid to electric transducer. More particularly the invention relates to an. improved fluid to electric transducer wherein a magnetic element is shifted in each of two directions by fluid means so as to operate a reed-type electrical switch.

1n the practical application of fluidics there are many occasions where it is desirable to be able to convert fluid pressure signals into corresponding electric signals. Several proposals have been made here however these proposals have not always been satisfactory from the standpoint of reliability, durability, cost or the ease with which such may be incorporated with other fluid control elements.

The primary object of the instant invention is to provide a novel fluid to electric transducer that is durable, reliable and relatively inexpensive.

Another object of the invention is to provide an improved fluid to electric transducer which, in being very rugged and compact, can be used in very hostile environments.

Another object of the invention is to provide a novel fluid to electric transducer which may be readily incorporated in a fluidic control system.

A further object of the invention is to provide an improved fluid to electric transducer whereby a reed-type electrical switch is operated by a movable magnet that is driven in each of two operative directions by two fluid-operating means.

Other objects of the invention will become apparent as the disclosure progresses.

In the drawings:

FIG. 1 is an axial sectional view of the instant transducer.

FIG. 2 is a fragmentary axial sectional view illustrating an active condition of some of the elements shown in FIG. 1.

Referring to FIG. 1 there is shown a main body member having a cylindrical bore 11 axially formed therethrough. Two end covers or caps 12 and 13 are sealingly secured by any suitable means to the opposite ends of said main body 10 so as to form two fluid chambers at the ends of said bore 11. The inner ends of the end caps are formed with central recesses 14 and 15 respectively which are adapted to receive and retain the end portions of an elongated glass-enclosed reed-type switch 16 that extends coaxially through said bore 11. The switch 16 is of a well-known type and thus all the structural details thereof need not be discussed here. In general however this switch includes a pair of magnetically sensitive reed contacts 17 and 18 that respectively 3,515,827 Patented June 2, 1970 extend out through the ends of the glass enclosure and through appropriate central holes formed in a pair of fittings 20 and 21. The fittings 20, 21 are centrally secured by any suitable means to and at the outer ends of the said end caps 11 and 12 and are made of any suitable electrical insulating material such as nylon, Delrin or the like.

An annular shaped permanent magnet 25 is mounted in the bore 11 and around the body portion of reed switch 16, and is arranged for axial movement along a portion of the length of said switch 16. To each radial face of said magnet 25 there is secured a disc-like washer 26 made of any suitable plastic material or the like. Washers 26 effectively afford smooth runnings seals first between the magnet 25 and the adjacent outer cylindrical surface of the reed switch 16, and secondly between the magnet 25 and the adjacent inner cylindrical walls of said bore 11. The axial right-hand limit of travel of the magnet 25 (as viewed in FIG. 1) is determined by engagement of the latter with a radially inwardly extending shoulder 27, while the axial left-hand limit of travel of the said magnet is determined by the engagement of the magnet with the inner end 30 of the end cap 12. When magnet 25 is in its first or left-hand position the remote and thus weak action of the magnetic field thereof allows the normally open switch contacts 17 and 18 to remain open. When magnet 25 is in its second or right-hand limit position the now stronger action of the magnetic field thereof causes the switch contacts 17, 18 to close, as illustrated in FIG. 2, due to induce magnetism in the reed contacts.

In order to permit magnet 25 to be shifted between its said rightand left-hand operative positions the main body 10 is formed with twofluid conduit apertures 31, 32 that are located adjacent the ends of bore 11 respectively. The apertures 31, 32 are connected through suitable fittings to the output lines 33 and 34 respectively of the two-stage fluidic power unit 35. The unit 35 comprises a pair of bistable wall attachment type fluid amplifiers 40 and 41, the output of amplifier 41 controlling the operation of amplifier 40. The construction and operation of each of the amplifiers 40 and 41 are wellknown and need not be discussed in detail here. The output leg 42 of amplifier 40 is connected to said conduit line 33 while the other output leg 43 thereof is connected to-said conduit line 34. Each of the amplifiers 40, 41 is operatively connected to a suitable source of fluid pressure S.

In the operation of the instant transducer when the fluidic control unit 35 is in a state wherein the output leg 43 is conducting the working fluid (such as air) the fluid pressure generated in the right end of bore 11 causes the magnet 25 to move to the left (as viewed in FIG. 1) and into its said first operative position whereby the electrical contacts 17 and 18 of switch 16 remain in their open condition shown in FIG. 1. When a control fluid pressure pulse or signal is received through the signal control line 44 of amplifier 41 the amplifier 40* Will be operatively switched so that said output leg 42 is conducting and thus directs pressure through line 33 and into the left-hand end of bore 11. At this time pressure fluid in the right end of bore 11 may exhaust through line 34 and said amplifier leg 43. Under these conditions said magnet 25 will be axially shifted to its second or right-hand operative position as is illustrated in FIG. 2 and in this displaced condition the magnetic field of the magnet 25 will cause the contact 17 and 18 to close and remain closed as shown in FIG. 2. This actuated condition of the parts will persist until a fluid pressure reset signal is applied through control line 45 of amplifier 41 at which time amplifier 40 will be restored to its other operative condition wherein output leg 43 is conducting. Here with fluid pressure applied to the right-hand end of. bore 11 and with the fluid pressure in the left-hand end of bore 11 now able to exhaust through line 33 the said magnet 25 will be displaced back to its said first or left-hand operative position so that the contacts 17 and 18 of switch may again assume an open condition. As will be apparent the successive alternate application of fluid pressure signals to the control lines 44 and 45 of amplifier 41 will cause the switch 16 to successively open and close; these fluid pressure signals thus being effectively converted into corresponding electrical signals at the contacts 17 and 18 of switch 16.

The instant apparatus has been found to operate reliably over long periods of use and is capable of operating at cyclic. speeds well above cycles per second.

Since many changes could be made in the embodiment of the invention as particularly described and shown herein without departing from the scope of the invention, it is intended that this embodiment be considered as exemplary and that the invention not be limited except as warranted by the following claims.

What I claim is:

1. A fluid to electric transducer comprising:

a main body having a cylindrical bore formed there through;

a glass-enclosed reed-type electrical switch disposed in said bore and having a non-conductive outer cylindrical surface and a pair of magnetically sensitive contacts;

an annular permanent magnet mounted for axial sliding movement in said bore and on said outer cylindrical surface of said reed-type switch, the two opposite limits of said axial movement of said magnet defining first and second operative positions of said magnet, the magnetic field of said magnet causing said switch contacts to close when said magnet is in its first operative position;

end caps connected to the ends of said main body so that a fluid chamber is formed at each end of said bore; and

fluid control means for admitting fluid pressure to one of said chambers and exhausting fluid pressure from the other of said chambers, and then for exhausting fluid pressure from said one chamber and supplying fluid pressure to said other chamber whereby said permanent magnet is alternately shifted to said first and second operative positions and said switch contacts are thereby alternately closed and opened. 2. Apparatus as defined by claim 1 wherein said fluid control means includes a first bistable fluid amplifier and a second fluid amplifier that is adapted to control the operation of said first fluid amplifier.

3. A fluid to electric transducer comprising:

a main body having a bore formed therethrough;

a reed switch disposed in said bore, said reed switch having a pair of magnetically sensitive electrical contacts;

means for retaining said reed switch in said bore;

an annular permanent magnet disposed in said bore and surrounding said switch, said magnet being movable along said switch between first and second operative positions for respectively opening and closing said switch contacts;

means defining a first fluid chamber at one end of said bore so that upon application of fluid pressure to said first fluid chamber said magnet may be displaced from said first to said second operative position;

means defining a second fluid chamber at the other end of said bore so that upon application of fluid pressure to said second chamber said magnet may be displaced from said second to said first operative position; and

fluid control means for alternately applying fluid pressure to said first and second fluid chambers, said fluid control means including a first fluid amplifier that is operatively coupled to control the fluid pressures for displacing said magnet, and a second fluid amplifier that is operatively coupled so as to control the operation of said first fluid amplifier.

4. Apparatus as defined by claim 10 wherein said first and second fluid amplifiers are bistable-type fluidic devices.

References Cited UNITED STATES PATENTS 2,055,815 9/1936 Dewey. 2,892,051 6/1959 Moore. 3,057,977 10/ 1962 Caswell. 3,200,214 8/ 1965 Aubert. 3,227,837 1/ 1966 Wcinstein. 3,363,073 1/ 1968 Bouguet.

ROBERT K. SCHAEFER, Primary Examiner J. R. SCOTT, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,515 827 Dated June 2; 1970 Inventor(s) Basil B. Beeken It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim l, line 1:

"10" should be i.

SIGNED Am i i-RED novmsm Amen:

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